In a large cooking pot, melt the butter. Slowly whisk in flour to make a roux. Gradually add the beer while whisking constantly to prevent lumps. The mixture should thicken. Add mustard and Worcestershire sauce. Still whisking, add the cheese in three batches, ensuring it is well melted each time. Pepper to taste.

Cut the garlic clove in two and rub the fondue pot. Toss the garlic clove into the melted cheese mixture.

Pour the fondue into the fondue pot and serve with baguette cubes, sausage chunks (Toulouse for me), and small boiled potatoes.